Expansion sleeve couplings are commonly used for shaft couplings in large turbine generators for many years. In such coupling structure, the hole diameters in both coupling flanges are same, which allows honing machining together. With the conical sleeve and the conical coupling design, each coupling hole will be completely fitted without any clearances and therefore each bolt can uniformly transmit the shaft torque. The assembly and dis-assembly of the expansion sleeve coupling with the available tools can be done easily and the robustness of this design has been demonstrated on several large turbine generators. FIG. 1 gives a schematic view of such expansion sleeve coupling design. The flanges of first shaft (i.e., the generator rotor shaft) and second shaft (i.e., the turbine rotor shaft) are attached with respective holes aligned. To achieve the shaft coupling, each bolt is installed with nuts engaged from both side A and side B. Therefore, this design of expansion sleeve couplings needs the access to both sides of the shaft coupling flanges.
Recently there develops a new type of shaft coupling in turbine generator, wherein the rotor shaft of the turbine is not directly coupled with the rotor shaft of the generator, but a hollow intermediate shaft is disposed and coupled therebetween. However, for the application of hollow intermediate shaft, the assembly and dis-assembly access is only possible from one side while not possible from the intermediate shaft side, and thus the current design of expansion sleeve coupling cannot be applied. The shaft coupling configuration including the hollow intermediate shaft will be described in more detail later with reference to FIG. 2.